Data processing: software development – installation – and managem – Software program development tool – Translation of code
Reexamination Certificate
1998-04-02
2001-07-03
Courtenay, III, -St. -John (Department: 2151)
Data processing: software development, installation, and managem
Software program development tool
Translation of code
C717S152000
Reexamination Certificate
active
06256776
ABSTRACT:
AUTHORIZATION
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
FIELD OF THE INVENTION
This invention relates generally to the field of digital signal type processors and more particularly to code development for execution by such processors.
DESCRIPTION OF THE RELATED ART
Many computer applications are incorporating mathematically intensive operations that are performance critical. For example, many image and speech processing applications must perform mathematically intensive operations, such as filtering, in real-time. Generally, such applications make use of a digital signal processor (DSP). As is well known, DSPs implement instructions that are particularly useful and efficient in digital signal processing applications. An example of a DSP is the TMS320 series of DSPs available from Texas Instruments. In addition to specialized DSPs, certain general purpose microprocessors incorporate DSP type instructions, such as the MMX instructions implemented by certain processors in the Pentium series of processors available from the Intel Corporation.
Traditionally, development of applications that execute efficiently on a DSP has required software developers that are highly skilled in both assembly language and sophisticated numerical analysis. The development of higher level languages and computer-aided software engineering (CASE) tools has simplified DSP program development to some extent. Compilers for programming languages such as the C programming language facilitate DSP code development by reducing or eliminating the need for programmers to be familiar with assembly language programming of a particular DSP. CASE tools such as the Simulink product available from the MathLab Corporation provide a prototyping bench for DSP code development, as well as for algorithm design.
Such tools however, do not address a very difficult part of the design process—the management of fixed point arithmetic. Development of programs that efficiently utilize fixed point capabilities of a DSP to generate numerically accurate results within the necessary time constraints is a critical aspect of DSP program development, and is one of the most difficult tasks faced by DSP programmers. Another difficult task is developing applications using floating point arithmetic where the word length of the underlying DSP is shorter than might be desired.
In many applications it is not necessary to understand the idiosyncrasies of fixed point math. Use of a floating point library in such applications, to utilize floating point circuitry within a DSP, simplifies code development and is an acceptable solution. DSPs with extensive floating point circuitry generally cost more than those without such support. Moreover, floating point operations take more time, for the same piece of hardware, than fixed point operations. This solution is therefore not acceptable when the application needs to run in real time at the fastest possible rate, or on the least expensive piece of hardware. Developing applications for DSPs in such situations requires either a very long development path, or the services of a rare, highly skilled DSP code developer. The result is higher development costs for DSP applications. What is needed therefore is a development environment that simplifies development of DSP code.
BRIEF SUMMARY OF THE INVENTION
In accordance with a principal aspect of the invention, code development for a target DSP is improved by way of a code library that provides fixed point functions with associated floating point functions that shadow the fixed point functions. The fixed point functions provide results that accurately match those provided by the target DSP. The floating point functions provide numerically accurate results that can be used as benchmark results for comparison with the results provided by the fixed point library. The code for the target DSP can then be modified to provide more accurate results from the fixed point libraries.
An advantage of certain preferred embodiments is that code generation for execution by fixed point circuitry of a DSP is simplified by providing a fast and easy comparison between desired numerical results, and actual results produced by the code on the target DSP. The target code can then be incrementally modified to provide results that are closer to the desired results. When the code is deemed to provide acceptable fixed point results, the code is recompiled to include only fixed point code. The floating point functions, and any debug functions are therefore not a part of the final production code. Code development is therefore simplified, allowing shorter development times and leading to lower development costs. Overall, recurring, system costs are also reduced by facilitating use of the least expensive hardware required for a particular application.
These and other features and advantages may be better understood by reference to the following detailed description.
REFERENCES:
patent: 5933641 (1999-08-01), Ma
patent: 5960201 (1999-09-01), Ma et al.
Bigrigg et al., “DSP Programming: It's Not Just Assembler Anymore,” Embedded Systems Programming, pp(5), Oct. 1995.
Courtenay III St. John
Fenwick & West LLP
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